Neurons in visual cortex exhibit a remarkable selectivity for certain features of the visual stimulus--a selectivity that must reflect an underlying specificity in the organization of their synaptic connections. Much of the anatomical specificity in cortical circuitry depends on the precise arrangement of intracortical axon arbors. For example, intrinsic axon arbors are responsible for interconnecting selected subsets of neurons that reside in different cortical layers; they are also responsible for selectively linking columns of neurons that share similar response properties. The proposed experiments focus on another dimension of intrinsic axonal connections which, while less conspicuous, may be no less important: the arrangement of axonal connections with respect to the map of visual space. The goal is to determine whether specificity in the topographic arrangement of intracortical axons, like laminar and modular specificity, plays a role in shaping the visual responses of cortical neurons. Previous studies have shown that individual cortical neurons often give rise to axon arbors that are elongated across the cortical surface, extending farther and giving rise to more terminals along one axis of the map of visual space than along the others. A combination of anatomical and physiological methods will be used to: (1) examine the relaxation between this anisotropy in connections and the preference of cortical neurons for oriented edges and (2) examine how this anisotropy might contribute to the response properties of cortical neurons. These experiments should provide new insights into the rules that govern the organization of local circuits in visual cortex--information that is crucial for understanding the neural basis of visual perception.